Sheet folding apparatus and image forming system incorporating same

A sheet folding apparatus configured to fold a sheet ejected from an upstream apparatus to which the sheet folding apparatus is coupled, the sheet folding apparatus comprising:

• a conveyance member configured to receive the sheet ejected from an ejection member of the upstream apparatus and convey the sheet in a sheet conveyance direction at either a first speed lower than a conveyance speed of the sheet by the ejection member or a second speed substantially same as or higher than the conveyance speed by the ejection member;
• a registration member configured to nip the sheet from the conveyance member and convey, at a timing, the sheet downstream in the sheet conveyance direction at either the first speed or the second speed;
• a pair of a first roller and a second roller configured to nip and convey the sheet from the registration member at either the first speed or the second speed, the pair of the first roller and the second roller configured to rotate in forward and reverse directions;
• a plurality of folding rollers disposed downstream from the second roller in the sheet conveyance direction and configured to rotate in forward and reverse directions to fold the sheet;
• and
• control circuitry configured to
• determine whether a length of the sheet in the sheet conveyance direction is equal to or smaller than a reference length, the reference length from an exit position from the ejection member to a folding operation start position downstream from the pair of the first roller and the second roller in the sheet conveyance direction;
• perform first-speed folding in which the conveyance member, the registration member, and the pair of the first roller and the second roller rotate at the first speed to fold the sheet, in response to a determination that the length of the sheet is equal to or smaller than the reference length;
• and
• perform second-speed folding in which the conveyance member, the registration member, and the pair of the first roller and the second roller rotate at the second speed to fold the sheet, in response to a determination that the length of the sheet is longer than the reference length.